J50, the ailing killer whale that has been the centre of attention for Canadian and American scientists throughout the summer, has been declared dead by one – but not all – research groups involved in rescuing the orca.

Her last known sighting was Friday, Sept. 7, according to the latest update by the U.S. National Oceanic and Atmospheric Administration and Department of Fisheries and Oceans Canada.

The Center for Whale Research, which declared J50 dead on Thursday afternoon, said it has had a vessel on the water for the past three days on the lookout for J50 but were unsuccesful. All other members of her family have been spotted during these outings.

But NOAA nor the DFO have declared the orca dead just yet.

“The U.S. Coast Guard is conducting aerial search and teams are searching by boat in likely locations in U.S. & Canadian waters. We have not given up,” NOAA said in a statement, urging anyone who sees the young orca to call the stranding hotline at 1-866-767-6114.

In previous updates, researchers have said it’s not unlike J50 to dissapear for several days before being spotted swimming alongside her mother.

The four year old has been suffering from parasitic worms and “peanut-head syndrome,” which means her head is smaller than her body due to malnutrition. Officials had been injecting J50 with broad-spectrum antibiotics, by way of dart gun, in hopes of bringing the ailing orca back to health.

Capture plan considered earlier this week

A rescue operation involving “hands-on physical examination” was part of discussions earlier this week on next steps possible to help J50 and her JPod.

On Wednesday, NOAA and the DFO said capturing J50, a four-year-old orca suffering from starvation, would only be an option if it didn’t harm other whales in J Pod and is the only option to allow her to contribute to the recovery of the population.

“The overriding priority of rescue is to evaluate, treat and rehabilitate J50 to give her the greatest chance of survival while ensuring her return and reunification with her family as soon as possible,” the agency said at the time.